1. Field of the Invention
The present invention relates to a head transport mechanism included in disc drive apparatuses, and more particularly, to a head transport mechanism for reciprocating a carriage in a radial direction of a disc using a linear motor as a drive source.
2. Description of the Related Art
For example, in a magnetic recording/reproducing apparatus for recording/reproducing information of a magnetic disc contained in a disc cartridge, a head transport mechanism for reciprocating a carriage in a radial direction of the magnetic disc is included. During the recording/reproducing, when the carriage is operated using a motor as a drive source, a magnetic head mounted on the carriage is reciprocated in the radial direction of the rotating magnetic disc.
Hitherto, a head transport mechanism using a linear motor as a drive source has been proposed, as disclosed in Japanese Unexamined Utility Model Publication No. 1-61877. In such a head transport mechanism, the linear motor is composed of yokes combining I-shaped yokes with U-shaped yokes, magnets fixed on the inner surface of the U-shaped yokes, and exciting coils disposed around the I-shaped yokes. Components of the yokes constituting a magnetic circuit of the linear motor are fixed on a support plate. Guide shafts are mounted to the support plate, a carriage having a head is guided by the guide shafts, and the exciting coils of the linear motor are fixed to both sides of the carriage.
In the thus constructed head transport mechanism, since propulsive force responsive to a direction of current flowing in the exciting coils is generated, the current flowing in the exciting coil is controlled, whereby the carriage is reciprocated in the radial direction of a disc along the guide shafts, so that information of the disc is recorded/reproduced by the head mounted on the carriage.
In the conventional head transport mechanism using the linear motor as the drive source, assembly steps are usually adopted such that the I-shaped yokes are inserted into the exciting coils fixed to the carriage after installing the carriage on the guide shafts and thereafter, the components of the magnetic circuit, including the I-shaped yoke, are secured on the support plate by screws.
However, since the head transport mechanism is disposed within a main chassis together with other components and the main chassis does not have enough space as is generally known, it is very difficult to adjust the I-shaped yokes to predetermined positions where they are secured by screws. In addition, when mounting the U-shaped yoke having magnets fixed on inner surfaces thereof, the I-shaped yokes are attracted by the magnets toward the U-shaped yokes so as to be brought into contact with the exciting coils, so that the exciting coils may be damaged.
In addition, when inserting the I-shaped yokes into the exciting coils, the exciting coils may be brought into contact with the I-shaped yoke and be damaged unless a lot of attention is paid. Thus, workability deteriorates.